This application claims a priority from German application 101 39 672.4, filed Aug. 11, 2001, and the contents of that application are incorporated herein by reference.
The invention relates to a method for inspecting an object, particularly a piece of luggage, in which radiation is emitted by a stationary radiation source while the object is transported in a straight line through the radiation and intensity levels of unabsorbed radiation are detected by a detector arrangement and processed into an image of the object, as well as to an apparatus for implementing such a method.
Processes and apparatus are known for inspecting objects, for example for security inspection of baggage at airports, wherein an object is transported in a straight line through radiation emitted by a stationary radiation source. The radiation not absorbed by the object is detected by a detector arrangement and processed into an image of the object, which is displayed on a screen for an operator. The inspection is typically performed using X-rays.
Since the unabsorbed radiation is detected in the inspection, a region in which the radiation is completely or almost completely absorbed is displayed on the image as a dark area. If it cannot be ruled out that another item, relevant from a security standpoint, is located behind the item that largely absorbs the radiation inside the object, a so-called xe2x80x9cdark alarmxe2x80x9d is triggered during the inspection. The object must then be subjected to an additional time-consuming security inspection; for example, suitcases are opened and examined manually.
An inspection system is disclosed in U.S. Pat. No. 6,088,423 that has three radiation sources that are arranged at different positions relative to a transport plane and emit radiation in three parallel planes. The radiation detected by three detector arrangements is processed by an analysis unit to determine probable outside contours of three-dimensional objects, one goal of which is to prevent false alarms.
An object of the invention is to provide a method and an apparatus for inspecting an object that permit improved inspection by reducing dark alarms with a low level of design complexity.
According to principles of this invention, with regard to the method, the object being inspected is rotated through an angle after a pass through radiation by a rotating device for changing its transport position and is subsequently transported through the radiation again with another image being produced. With regard to the apparatus, a transport device has the rotating device for rotating the object after the pass through the radiation to change its transport position.
According to the invention, only a single stationary radiation source is required. If the image generated by the first pass contains dark areas to be inspected, the object being inspected is rotated into a different transport position and an additional image is generated by the same radiation source. This process, controlled manually by an operator or automatically by a machine, can be repeated as many times as necessary until sufficient information has been obtained about the dark area in the first image.
In the simplest embodiment, an operator decides, based on the images available to him, whether and in what position the object is to be re-transported through the radiation and re-inspected. The analysis unit prepares the individual images of an object appropriately for this decision; preferably they are displayed next to each other or sequentially on a screen, and all facing in the same direction.
To provide as much support as possible to an operator for manual control of the inspection, current status parameters, or values, of the inspection process are displayed, in particular the angular position of the object and the number of passes that have been made through the radiation. Preferably the information is displayed on the screen of the analysis unit, although a separate display is also possible.
In a further enhanced embodiment, the process can be automated such that the discovery of a dark area triggers an automatic inspection routine. To this end, a computer automatically controls the number of passes and/or the angle of a pass as a function of parameters of the dark area. The particular angle of rotation and the chronological sequence of the display of the individual images of an object can be chosen such that the impression of a rotating object is produced on the screen. This type of display makes it easier for the operator viewing the image to decide whether the object should undergo another inspection stage or be examined manually as well.
In principle, rotation about all three spatial axes is possible in order to change the position of the object before another pass. Preferably, a direction of the rotational axis and a size of the angle are chosen such that the probability is greatest that no dark area will be produced on the next pass.
In the simplest embodiment, the object is rotated about only one axis. In this case, rotation about an axis perpendicular to the transport plane is preferred, since this can be accomplished with the least expense.
Preferably the object""s direction of transport through the radiation is reversed each time, with an image generated at each pass through the radiation. Alternatively, it is also possible to produce images only during transport in a single direction. This simplifies analysis of the images for line-by-line detection, since they are all produced in the same direction relative to the radiation and thus can be displayed directly. To this end, either the object is not inspected when it is transported backward in a straight line past the radiation source, or the object is transported back for the next pass on a transport loop that leads outside and around the radiation source.